JP5214776B2 - Vulcanized tread - Google Patents

Description

  The present invention relates to a vulcanized tread, and in particular, a base tire serving as a base of a tire and a vulcanized tread attached to the base tire are individually molded, and the base tire and the vulcanized tread are formed. The present invention relates to a vulcanized tread capable of suppressing uneven wear of integrally manufactured tires.

One method of manufacturing a tire is to separately form a base tire that serves as a base of the tire and a vulcanized tread that is attached to the outer peripheral surface of the base tire and constitutes the tread of the tire. There is known a method of obtaining a product tire by integrating a tire and a tread.
The base tire is obtained, for example, by removing a tread portion of a used tire with a buffing device, and the surface after removing the tread portion is formed as a sticking surface for sticking a new tread. In forming the sticking surface, the grinder cutting part is brought into contact with the tread part of the used tire fixed in a non-rotatable state with the internal pressure applied to the drum constituting the buffing device. Specifically, by repeatedly moving the grinder in the width direction of the used tire while rotating the drum, the radius of curvature decreases from the center in the tire width direction toward the both ends in the cross section in the width direction. To a predetermined shape. The tires with the predetermined shape are attached to the tires with a constant thickness or a vulcanized tread that is thinly formed from the center in the width direction toward both ends. This completes the product tire.

JP-A-9-70903 JP 2001-180228 A

However, as described above, the sticking surface of the base tire is formed so that the radius of curvature becomes smaller from the center in the width direction toward both ends, so that the vulcanized tread having a constant thickness or the width from the center in the width direction. When a vulcanized tread that is thinned toward both sides in the direction is affixed, the vulcanized tread will bend in the width direction, and the groove that is formed in the vulcanized tread is continuous in the longitudinal direction (main groove) Is expanded in the width direction, and the radius difference between the inner edge and the outer edge of the groove is increased.
In particular, in the groove located at the outermost part of the vulcanized tread, the radius difference becomes larger compared to the diameter change at the edge of the other groove, and as a result, the contact length becomes longer than the contact length assumed at the time of tire design. When the tire is used, uneven wear tends to occur on the outer side in the width direction of the tread. In addition, in the formation of the sticking surface of the base tire, the tread part of the used tire is buffed with the bead part wider than the rim width when the wheel is assembled. Depending on the case, when the finished product tire is assembled to the wheel, the tread surface shape of the tread may be larger than the buffing shape. In this case, the radius on the tread end side is likely to be smaller than the radius on the tread center, and the tread width direction end side is extremely shorter than the contact length assumed when designing the tire, and vulcanized when using the product tire Uneven wear tends to occur at the center in the width direction of the tread.

  An object of the present invention is to provide a vulcanized tread capable of suppressing uneven wear of a tire formed by sticking a vulcanized tread to a sticking surface of a base tire in order to solve the above problems. To do.

As a configuration of the vulcanized tread for solving the above-mentioned problem, a plurality of grooves extending in the longitudinal direction are provided in the width direction, and the cross-sectional thickness of the outermost groove located on the outermost side in the width direction from the equator, And gradually increasing from the outer end of the outermost groove in the width direction to the outer side in the width direction.
According to this configuration, the cross-sectional thickness of the vulcanized tread having a plurality of grooves extending in the longitudinal direction in the width direction gradually decreases from the equator to the equator-side groove end of the outermost groove located in the outermost width direction. And since it increases gradually from the width direction outer side groove end of the outermost groove to the width direction outer side, the contact shape when the tread of the product tire to which the vulcanized tread is applied contacts the road surface can be optimized.
That is, when the internal pressure is applied to the product tire to which the vulcanized tread is applied by gradually decreasing the cross-sectional thickness from the equator to the equator side groove end of the outermost groove located in the outermost width direction, the tread of the tire is applied. The cross-sectional shape at can be a smooth curve. Further, by gradually increasing the cross-sectional thickness from the widthwise outer groove end of the outermost groove to the widthwise outer side, it is possible to prevent the widthwise outer side from being in contact with the road surface. Therefore, since the tread of the product tire and the road surface are grounded in a well-balanced manner, uneven wear of the tread can be suppressed.

In addition, as another configuration of the vulcanized tread, a plurality of longitudinally extending grooves are provided in the width direction, and the cross-sectional thickness gradually decreases from the equator to the equator side groove end of the outermost groove located in the outermost width direction. The outermost groove is configured to be constant from the width direction outer side groove end to the width direction outer side.
According to this configuration, the cross-sectional thickness of the vulcanized tread having a plurality of grooves extending in the longitudinal direction in the width direction gradually decreases from the equator to the equator-side groove end of the outermost groove located in the outermost width direction. Since the outermost groove is constant from the widthwise outer groove end to the widthwise outer side, it is possible to optimize the contact shape when the tread surface of the product tire to which the vulcanized tread is applied contacts the road surface. .
That is, when the internal pressure is applied to the product tire to which the vulcanized tread is applied by gradually decreasing the cross-sectional thickness from the equator to the equator side groove end of the outermost groove located in the outermost width direction, the tread of the tire is applied. The cross-sectional shape at can be a smooth curve. Moreover, it can prevent that the width direction outermost end touches a road surface too much by being constant from the width direction outer side groove end of a outermost groove to the width direction outer side. For example, a product tire in which a tread is applied to a base tire having a low flatness ratio is applied to an outer groove end in the width direction of the outermost groove when an internal pressure is applied compared to a product tire applied to a base tire having a high flatness ratio. The change in diameter is small. For this reason, by making the cross-sectional thickness constant from the width direction outer side groove end of the outermost groove to the width direction outer side, it is possible to prevent the width direction outer side groove end from being in contact with the road surface excessively or being ungrounded. That is, since the tread surface of the product tire and the road surface are in contact with a good balance, uneven wear of the tread can be suppressed.

As another configuration of the vulcanized tread, the cross-sectional thickness at the outermost end in the width direction is thinner than the cross-sectional thickness at the equator.
According to this configuration, since the cross-sectional thickness at the outermost end in the width direction is thinner than the cross-sectional thickness at the equator, when the product tire contacts the road surface, the contact length in the tire circumferential direction at the equator is the longest. Therefore, the ground contact shape between the tread and the road surface in the product tire is ideal. That is, since the tread is not caught on the road surface, the rolling resistance is reduced, and uneven wear does not occur in the tread.

As another configuration of the vulcanized tread, the cross-sectional thickness at the equator-side groove end of the outermost groove is equal to the cross-sectional thickness at the outermost end in the width direction.
According to this configuration, since the cross-sectional thickness at the equator-side groove end of the outermost groove is equal to the cross-sectional thickness at the outermost end in the width direction, when the product tire contacts the road surface, the outermost width direction of the vulcanized tread It is possible to prevent the end from being grounded and excessive.

FIG. 2 is a perspective view and an exploded view of a tire in which a tread is attached to a base tire. It is the external appearance perspective view and cross-sectional view of the width direction of a tread. It is a top view of a tread. It is an enlarged view of a tread cross section. It is sectional drawing of the other form of a tread. It is a figure which shows the comparative example of the tread vulcanized and molded based on this invention and the conventional tread. It is a figure which shows the comparative example of the other form of the tread vulcanized-molded based on this invention, and the conventional tread.

  Hereinafter, the present invention will be described in detail through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included in the invention. It is not necessarily essential to the solution, but includes a configuration that is selectively adopted.

FIG. 1A shows an exploded perspective view of a product tire formed by sticking a tread 1 according to the present invention to a base tire 2, and FIG. 1B shows the tread 1 through an adhesive layer 3. Sectional drawing of the product tire stuck on the base tire 2 is shown. FIG. 2 shows an external perspective view of the tread 1 and a cross-sectional view in the width direction. FIG. 3 shows a plan view of the tread 1.
As shown in FIGS. 1A and 1B, the tread 1 according to the present invention is attached via an adhesive layer 3 formed on the outer peripheral surface of the base tire 2. As shown in FIG. 2, the tread 1 is vulcanized and molded into a belt having a predetermined size. The cross-sectional shape in the width direction (short direction) of the tread 1 is a substantially trapezoidal shape, and the non-tread surface 1a side attached to the base tire 2 is linearly formed, and the tread surface 1b side that contacts the road surface is formed in a wave shape. .
A plurality of main grooves M1; M2 extending along a circumferential direction (longitudinal direction) when the tread 1 is attached to the base tire 2 and adjacent main grooves M1; M2 and main grooves M1 ; Width direction groove | channel N1; N2; N3 which connects M1 in the width direction of the tread 1 is formed.
The main groove M1 is located on the equator side which is the center in the width direction, and the main groove M2 is an outermost groove located on the outer side in the width direction than the main groove M1. For example, a wear indicator indicating the wear limit of the tread 1 is formed on the groove bottom of the main groove M1; M2 (JIS D 4230).

The width direction grooves N1; N2; N3 have, for example, the same depth as the main grooves M1; M2, and are formed periodically or aperiodically along the longitudinal direction. The tread 1b of the tread 1 according to the present embodiment is partitioned into a block shape by a plurality of main grooves M1; M2 and a plurality of widthwise grooves N1; N2; N3.
As shown in FIGS. 2 and 3, a width direction groove N1 connects the main grooves M1; M1 to the tread surface 1b on the side that contacts the road surface, and is formed periodically or aperiodically along the longitudinal direction. As a result, the center block 5 defined by the width direction grooves N1; N1 is formed in the center portion of the tread 1 in the width direction. In addition, a width direction groove N2 is formed on the tread 1b by connecting the main grooves M1; M2 to each other and periodically or aperiodically along the longitudinal direction. Side blocks 6 defined by the grooves N2; N2 are formed.
Further, the tread surface 1b has a width direction groove N3 that connects the main groove M2 and a tread side end surface S (hereinafter referred to as a side end surface S) and is formed periodically or aperiodically along the longitudinal direction. The shoulder block 7 defined by the width direction grooves N3; N3 is formed outside the side block 6 in the width direction.
In the present embodiment, to simplify the description, the tread pattern is described as being symmetrical with respect to the equator P1 (hereinafter referred to as the width direction center P1) that is the center of the tread width direction shown in FIGS. The specific tread pattern mode is not limited to this.

FIG. 4 shows an enlarged view of a cross section in the width direction of the tread 1 in AA of FIG. Hereinafter, the thickness in the width direction of the tread 1 having the tread blocks 5; 6; 7 will be described with reference to FIGS.
As shown in FIGS. 3 and 4, the center block 5 is located at the center of the tread 1 in the width direction and is formed across the width direction with the width direction center P <b> 1 interposed therebetween.

The thickness H2 from the non-tread surface 1a to the tread surface 1b at the edge P2 on the side of the center P1 in the width direction of the main groove M1 that divides the center block 5 and the side block 6 is from the non-tread surface 1a to the tread surface 1b at the tread center P1. It is set to be thinner than the thickness H1. The edge P2 is an equatorial groove end (equatorial groove end) where the main groove M1 opens on the tread surface 1b side.
Further, the thickness H3 from the non-tread surface 1a to the tread surface 1b at the end edge P3 on the outer side in the width direction of the main groove M1 is formed to be thinner than the thickness H2 at the end edge P2. The edge P3 is an outer groove end (outer groove end) where the main groove M1 opens on the tread surface 1b side.
The thickness H4 from the non-tread surface 1a to the tread surface 1b at the edge P4 on the side of the center P1 in the width direction of the main groove M2 that divides the side block 6 and the shoulder block 7 is more than the thickness H3 at the end edge P3. Thinly formed. The edge P4 is an equatorial groove end (equatorial groove end) where the main groove M2 opens on the tread surface 1b side.

  That is, the tread 1 according to the present embodiment is formed such that the cross-sectional thickness in the width direction is the thickest at the width direction center P1, the thickness H1 being the largest, and then gradually becoming thinner with the edges P2, P3, and P4. More specifically, the cross-sectional thickness smoothly and gradually decreases in the width direction from the width direction center P1 to the edge P4 on the width direction center P1 side in the outermost main groove M2 in the width direction of the tread 1. Formed.

By forming the thickness from the width direction center P1 of the tread 1 to the end edge P4 as described above, the tread 1 is placed in the width direction on the sticking surface formed like a bow of the base tire 2. Even if it is bent and stuck along, a virtual line connecting the edges P2, P3, and P4 in the tread block 4 becomes a smooth curve that monotonously decreases from the width direction center P1 to the edge P4. Specifically, when the tread 1 is attached to the attachment surface, the edge P2 and the edge P3 of the main groove M1 have a radius while separating the distance from each other due to the curvature in the width direction of the attachment surface. Although the thickness of the edge P2 and the edge P3 in the tread 1 is gradually reduced gradually, the edge P2 and the edge P3 do not become angled, and the width direction The center is smooth from P1 to P3. Since the thickness gradually decreases from the width direction center P1 of the center block 5 to the end edge P2 and from the end edge P3 of the side block 6 to the end edge P4, in the tread of the product tire to which the tread 1 is applied. The shape gradually decreases gradually from the width direction center P1 to the edge P4.
The cross-sectional shape line connecting the edge P2; P3; P4 from the center P1 in the width direction is preferably formed to be a smooth curve that approximates a buff line, for example, but stepwise in the same block, for example. Alternatively, it may be a linearly extending shape, and the thickness reduction rate can be arbitrarily set.

Next, the cross-sectional thickness outside the edge P4 in the width direction will be described.
A thickness H5 from the non-tread surface 1a to the tread surface 1b at the edge P5 on the outer side in the width direction of the main groove M2 is formed thinner than, for example, the thickness H4 at the aforementioned edge P4. The edge P5 is a groove end (width direction outer groove end) on the outer side in the width direction of the main groove M2 opened on the tread surface 1b side. The thickness H6 from the non-tread surface 1a to the tread surface 1b at the end edge P6 on the tread surface 1b side of the side end surface S of the tread 1 is formed to be thicker than the thickness H5 of the end edge P5. The edge P6 is the outermost end in the width direction of the tread surface 1b where the tread surface 1b and the side end surface S are connected.
More specifically, the thickness H5 at the outer edge P5 in the width direction of the main groove M2 is formed to be thinner than the thickness H4 at the edge P4, and the cross-sectional thickness from the edge P5 to the outermost edge P6 in the width direction. The thickness is gradually increased, and the thickness H6 at the edge P6 is formed to be the same as the thickness H4 at the edge P4.
In other words, the thickness gradually increases from the edge P5 so that the thickness H6 at the edge P6 is equal to the thickness H4 at the edge P4. Further, in the cross-sectional shape, a shape line connecting the end edge P5 and the end edge P6 is set as a straight line, for example.

As described above, the thickness H5 at the outer edge P5 of the main groove M2 is formed to be thinner than the thickness H4 at the edge P4, thereby sticking the tread 1 along the curvature of the sticking surface. Even so, the edge P4 and the edge P5 of the main groove M2 do not have a corner, and a smooth curve is formed from the width direction center P1 to the edge P5.
In addition, the thickness is gradually increased from the outer edge P5 of the main groove M2 located at the outermost edge of the tread 1 to the edge P6 which is the outermost edge in the width direction. Even if it is bent and stuck along the shoulder portion of the base tire 2 having a large curvature change on the surface, it can be stuck so as to have an optimum curve from the edge P5 to the edge P6. That is, when the tread 1 is stuck to the sticking surface, a radius difference in the product tire tends to occur between the edge P5 and the edge P6 due to a large curvature change of the sticking surface in the shoulder portion of the base tire 2. Since the thickness gradually increases from the edge P5 to the edge P6, the radius difference can be reduced. Further, by forming the thickness H6 at the edge P6 so as to be the same as the thickness H4 at the edge P4, when the tread 1 is adhered to the adhesion surface, the edge 5 from the edge P4 to the edge 5 is obtained. A smooth curve can be obtained up to the edge P6 through the above. Therefore, when the product tire to which the tread 1 is applied contacts the road surface, it is possible to prevent the edge P6 which is the outermost end in the width direction of the tread surface 1b of the vulcanized tread from being excessively grounded.

  The tread 1 is formed so that the cross-sectional thickness is constant in the longitudinal direction at an arbitrary position in the width direction while maintaining the above-described thickness relationship in the width direction. That is, the shape of the tread surface 1b when the tread 1 is cut in the width direction at an arbitrary position in the longitudinal direction is formed to be the same.

  FIG. 5 is a cross-sectional view showing another form of the tread 1. In the above-described embodiment, the cross-sectional thickness of the tread 1 is formed so as to gradually increase from the end edge P5 to the end edge P6. However, in this embodiment, the cross-sectional thickness from the end edge P5 to the end edge P6 is constant. It is different in point.

  As shown in the figure, in the tread 1 according to the present embodiment, the cross-sectional thickness in the width direction is such that the thickness H1 at the center P1 in the width direction is the largest, and then gradually becomes thinner with the edges P2, P3, and P4 in order. And the thickness H5 at the edge P5 is made thinner than the thickness H4 at the edge P4, and the thickness H6 from the edge P5 to the edge P6 which is the outermost edge in the width direction is a constant thickness. Formed to be. That is, the cross-sectional shape from P5 to P6 is a straight line.

  According to the present embodiment, the thickness is constant from the end edge P5 to the end edge P6 on the side end face S side of the main groove M2 located on the outermost side in the width direction of the tread 1 so as to be flat. Even if it is applied to the base tire 2 having a low rate and bent along the shoulder portion of the base tire 2 having a large change in curvature on the sticking surface, it is made an optimum curve from the edge P5 to the edge P6. Can do. That is, the base tire 2 with a small flatness has a smaller change in the curvature of the sticking surface at the shoulder portion which is the outermost portion in the width direction when an internal pressure is applied as compared with the base tire 2 with a large flatness. By making the thickness from P5 to the edge P6 constant, when the product tire is manufactured by applying the tread 1 to the base tire 2 having a small flatness, the edge 5 to the edge P6 is smooth. When the product tire contacts the road surface, the edge P6 which is the outermost end in the width direction of the tread 1 can be prevented from being excessively grounded. Therefore, since the tire to which the tread 1 of the present embodiment is adhered is grounded in a well-balanced manner with respect to the road surface when the tread surface 1b is in contact with the road surface, uneven wear of the tread 1 on the tire can be suppressed.

The tread 1 according to each of the above embodiments is formed by, for example, a press-type vulcanizer.
Although not shown, the vulcanizer includes a tread-side mold that molds the tread 1 side of the tread 1 and a non-tread-side mold that molds the non-tread 1a side, and is formed by both molds. By accommodating a tread member formed in a band shape in advance in the space, the apparatus can be heated in a state where a certain pressure is applied.
On the surface of the tread-side mold, irregularities having a shape obtained by inverting the shape of the tread pattern of the tread 1 are formed, and the surface of the tread member is pressed against the surface of the tread-side mold so that a desired tread is formed. A tread 1 having a pattern can be obtained. Further, the surface of the non-treading surface side mold is formed as a flat surface, and the surface facing the flat surface is formed as the non-treading surface of the tread 1.

  Hereinafter, an outline of a process for manufacturing a product tire by sticking the tread 1 having the above-described cross-sectional thickness to the base tire 2 will be described. The base tire 2 shown in FIG. 1 can be obtained, for example, by removing a tread portion of a used tire by a buffing device not shown. Although not shown, the buffing device can cut a tread portion of a used tire that is installed opposite to the drum that can hold the used tire in a state where an internal pressure is applied, and is rotated by the drum. And a grinder having a cutting portion. The drum is a cylindrical body composed of a plurality of drum pieces connected so as to be able to expand and contract, and is capable of holding used tires having different sizes in a non-rotatable manner. In addition, a flange portion is formed on the outer peripheral surface of the drum so as to be spaced apart by a certain distance in the width direction. The flange portion corresponds to a rim flange of the wheel, and a pair of bead portions are firmly fixed on the flange portion when an internal pressure is applied to the used tire.

  The grinder is installed so as to be movable in the direction close to or away from the used tire held by the drum and in the width direction of the used tire. Then, the grinder is brought close to the tread portion of the rotating used tire, and the tread portion is gradually cut by moving the cutting portion in the width direction while contacting the tread portion, and has a predetermined shape (buff line). The base tire 2 which has a sticking surface can be obtained.

  The adhesive layer 3 is disposed on the sticking surface formed along the circumferential direction of the base tire 2 obtained through the above steps. The adhesive layer 3 is made of unvulcanized rubber called cushion rubber, and is formed by discharging the rubber so as to have a uniform thickness along the sticking surface by, for example, an extrusion molding machine.

The above-described tread 1 is wound around the circumferential direction on the sticking surface of the base tire 2 on which the adhesive layer 3 is disposed.
That is, the tread 1 is preliminarily integrated with the base tire 2 via the adhesive layer 3. Next, the pre-integrated tread 1 and the base tire 2 are accommodated in a sealed bag called an envelope.
The envelope has a valve capable of degassing the internal air, and after the tread 1 and the base tire 2 are accommodated, the internal air is deaerated through the valve so that the surface of the envelope is tread 1 and the base tire 2. Adhere to the surface. Then, the tread 1 and the base tire 2 in a state where pressure is applied by the envelope are carried into a vulcanizer called a vulcanizer. The cushion rubber as the adhesive layer 3 in the tread 1 and the base tire 2 carried into the vulcanizer is placed in a state in which a predetermined pressure and temperature are applied for a certain period of time, so that vulcanization proceeds, and the tread 1 and the base tire 2 are firmly integrated to complete the production of the product tire.

Example 1
6A shows a cross-sectional shape of a tread 1 vulcanized and molded according to the present invention, and FIG. 6B shows a cross-sectional shape of a conventional tread 10 having a constant cross-sectional thickness. . FIG. 6C shows the ground contact shape of the product tire to which the tread 1 according to the present invention is applied, and FIG. 6D shows the tire ground contact shape to which the conventional tread 10 is applied. FIG. 6 (e) is a table showing the difference in the length of the contact length in the contact shape of FIGS. 6 (c) and 6 (d). In the table, the ground contact length is indicated by the ground contact length L1 in the tire circumferential direction at the tread center P1 as a reference (100), and the ground contact lengths L4 to L6 at the respective edges P4 to P6 are shown as a ratio to the ground contact length L1. .
In Example 1, a tread 1 according to the present invention and a tread 10 vulcanized and molded as a comparative example were attached to a base tire 2 buffed with a 275 / 80R22.5 used tire, respectively. Product tires were prototyped and subjected to comparative tests.

As shown in FIG. 6A, the tread 1α (1) according to the first embodiment has a width of 250 mm on the non-tread surface 1a side, a thickness H1 of the width direction center P1 of 18.8 mm, and a thickness of the edge P4. H4 is 18.3 mm, the thickness H5 of the edge P5 is 17.8 mm, the thickness H6 of the edge P6 is 18.3 mm, and the cross-sectional thickness from the center P1 in the width direction to the edge P4 has a smooth curved shape The cross-sectional thickness from the end edge P5 to the end edge P6 is set so that the cross-sectional thickness of the end edge P5 is set smaller than the end edge P4. Is formed in a shape that gradually increases linearly.
As shown in FIG. 6B, the tread 10α (10) according to the comparative example is formed in a constant flat plate shape with a thickness from the width direction center P1 to the edge P6 being 18.8 mm.

Hereinafter, the tire with the tread 1α attached will be described as a product tire A, and the tire with the tread 10α attached will be described as a product tire B.
As shown in FIG. 6C, FIG. 6D, and FIG. 6E, it can be seen that the product tire A matches the target shape (contact length) assumed at the time of tire design. That is, the cross-sectional thickness of the tread 1α gradually decreases from the width direction center P1 to the edge P4 on the width direction center P1 side of the main groove M2 located at the outermost side in the width direction, and the edge P5 that is the outer groove end of the main groove M2. The product tire A having a desired grounding shape can be manufactured by molding so as to increase gradually from the outer end in the width direction. In particular, uneven wear was not observed because the tread surface 1b had a desired shape on the outer side in the width direction of the main groove M2 with the largest diameter change in the state where the internal pressure was applied. Therefore, the product tire A to which the tread 1α of the present invention is applied is a tire having a small rolling resistance and having the performance at the time of designing the tire without causing uneven wear.
On the other hand, the product tire B tends to have a generally longer contact length than the target assumed at the time of designing the tire. In particular, the contact length L5 at the edge P5 is larger than the contact length L1 at the center P1 in the width direction. It is getting longer. In other words, the product tire B to which the tread 10α is adhered is a result of the end edge P5 being locally strongly pressed against the road surface, so that the entire tire does not wear uniformly, and uneven wear occurs in the portion. It became. Such uneven wear becomes a factor of increasing rolling resistance and causes instability during maneuvering.

Example 2
7A shows a cross-sectional shape of a tread 1 vulcanized and molded according to the present invention, and FIG. 7B shows a cross-sectional shape of a conventional tread 10 having a constant cross-sectional thickness. . FIG. 7 (c) shows the ground contact shape of the product tire to which the tread 1 according to the present invention is applied, and FIG. 7 (d) shows the ground contact shape of the tire to which the conventional tread 10 is applied. FIG. 7 (e) is a table showing the difference in the length of the contact length in the contact shape of FIGS. 7 (c) and 7 (d). In the table, the ground contact length is indicated by the ground contact length L1 in the tire circumferential direction at the tread center P1 as a reference (100), and the ground contact lengths L4 to L6 at the respective edges P4 to P6 are shown as a ratio to the ground contact length L1. .
In Example 2, a tread 1 according to the present invention and a tread 10 formed by vulcanization as a comparative example are used for a base tire 2 in which a used tire of 11R22.5 having a tire size different from that in Example 1 is buffed. The product tire was prototyped and a comparative test was conducted.

As shown in FIG. 7A, the tread 1β (1) according to the second embodiment has a non-tread surface 1a side width of 230 mm, a tread center P1 thickness H1 of 18.8 mm, and an edge P4 thickness H4. Is 18.3 mm, the thickness H5 of the edge P5 is 17.8 mm, the thickness H6 of the edge P6 is 17.8 mm, and the cross-sectional thickness from the center P1 in the width direction to the edge P4 gradually decreases in a smooth curved shape. In addition, the cross-sectional thickness of the end edge P5 is set to be thinner than the end edge P4, and the cross-sectional thickness from the end edge P5 to the end edge P6 is made constant.
As shown in FIG. 7B, the tread 10β (10) according to the comparative example is formed in a constant flat plate shape with a thickness from the width direction center P1 to the edge P6 being 18.8 mm.

Hereinafter, the tire with the tread 1β attached will be described as a product tire A, and the tire with the tread 10β attached will be described as a product tire B.
As shown in FIG. 7C, FIG. 7D, and FIG. 7E, it can be seen that the product tire A matches the target shape (contact length) assumed at the time of tire design. That is, the cross-sectional thickness of the tread 1β gradually decreases from the width direction center P1 to the edge P4 on the width direction center P1 side of the main groove M2 located on the outermost side in the width direction, and the edge P5 on the outer side in the width direction of the main groove M2. The product tire A having a desired grounding shape can be manufactured by forming it uniformly from the edge P6 that is the outermost end in the width direction to the edge P6. In particular, the product tire A of this example has a higher flatness than the product tire A of Example 1, and therefore, by molding the product tire A uniformly from the outer edge P5 of the main groove M2 to the outer end in the width direction. When the inner pressure was applied, uneven wear was not observed because the tread surface 1b had a desired shape on the outer side in the width direction than the main groove M2 having the largest change in tire diameter. Therefore, the product tire A to which the tread 1β of the present invention is applied is a tire having a small rolling resistance that has performance at the time of tire design and does not cause uneven wear.
On the other hand, the product tire B of the present example has a higher flatness ratio than the product tire B of Example 1, so that the contact length is longer on the outer side in the width direction of the tread 10β than the target value assumed at the time of tire design. In particular, the contact length L6 at the edge P6 is much longer than the target value. That is, the product tire B to which the tread 10β is stuck is that the shoulder block 7 is strongly pressed against the road surface, so that the entire tire does not wear uniformly, and uneven wear occurs particularly at the edge P6. became. Such uneven wear becomes a factor of increasing rolling resistance and causes instability during maneuvering.

As described above, in the tread 1β, the cross-sectional thickness gradually decreases from the width direction center P1 to the edge P4 on the width direction center P1 side of the main groove M2 located on the outermost side in the width direction, and according to the tire flatness Thus, by gradually increasing or making the thickness of the edge P6, which is the outer edge in the width direction, from the outer edge P5 of the main groove M2, uneven wear of the tread 1 when a product tire is made can be prevented. . That is, when the flatness of the base tire is small, the thickness H6 of the edge P6 that is the outermost edge in the width direction is gradually increased from the outer edge P5 of the main groove M2, and when the flatness of the base tire is small, the main groove Uneven wear of the tread 1β can be prevented by making the thickness H6 of the edge P6, which is the outer edge in the width direction, constant from the outer edge P5 of M2.
Further, by appropriately setting the thickness H5 of the end edge P5 with respect to the thickness H4 of the end edge P4 to be the same or thicker, an edge effect can be obtained on the outer side in the width direction that is the tire shoulder portion. And stability can be improved.

In the above-described embodiment, the tread 1 is described as being formed into a belt shape, but is not limited to the belt shape, and may be an annular tread that is preliminarily annularly vulcanized.
Further, in the above embodiment, the base tire is formed by buffing the tread portion worn from the used tire, but it is formed by buffing the crown portion of the base tire vulcanized and molded as a new base tire. It may be good.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

1; 1α; 1β tread, 1a non-tread surface, 1b tread surface, two tires, 3 adhesive layer,
4 tread blocks, 5 center blocks, 6 side blocks,
7 Shoulder block, H1 to H6 thickness, L1; L4; L5; L6 Ground contact length,
M1; M2 main groove, N1; N2; N3 width direction groove, P1 tread center,
P2 to P6 edge.

Claims (4)

A plurality of grooves extending in the longitudinal direction are provided in the width direction,
A vulcanized tread in which the cross-sectional thickness gradually decreases from the equator to the equator-side groove end of the outermost groove located at the outermost side in the width direction, and gradually increases from the widthwise outer groove end to the widthwise outer side of the outermost groove. A plurality of grooves extending in the longitudinal direction are provided in the width direction,
A vulcanized tread whose cross-sectional thickness gradually decreases from the equator to the equator-side groove end of the outermost groove located at the outermost side in the width direction, and is constant from the widthwise outer groove end to the widthwise outer side of the outermost groove.   The vulcanized tread according to claim 1 or 2, wherein a cross-sectional thickness at the outermost end in the width direction is thinner than a cross-sectional thickness at the equator.   The vulcanized tread according to any one of claims 1 to 3, wherein a cross-sectional thickness at the equator-side groove end of the outermost groove is equal to a cross-sectional thickness at the outermost end in the width direction.

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